The preparation and use of crosslinkable LC siloxanes is exemplified by U.S. Pat. No. 5,211,877. These compounds comprise primarily property-determining mesogens and selectable proportions of constituents of the molecule which firstly contribute to the mesogenic properties of the LC organosiloxanes but secondly are capable, by virtue of pendant polymerizable groups, of irreversibly fixing--by means of three-dimensional crosslinking--certain chemical and physical properties which are characteristic of the LC silicones thus prepared. Depending on the nature and amount of admixture of further, copolymerizable mesogens and other constituents it is thus possible on crosslinking to prepare, for example, pigments whose color is based on the cholesteric phase of a copolymerized, optically active mesogen and/or on the addition of added mesogens.
When the LC organosiloxanes specified in U.S. Pat. No. 5,211,877 are employed as LC pigments they give different colors at processing temperatures of 130.degree., which is for example a customary processing temperature for the OEM finishing of steel panels, and, alternatively, when processed at 80.degree. C., a customary processing temperature for refinishes. This differing behavior is brought about by the glass temperature of the pigment in conjunction with its swelling in the course of the preparation of coating materials, and the unswelling process when these coating materials are dried; in other words, by the action of solvents on the pigment. The swelling process, and the leaching of uncrosslinked constituents from the pigment, which may take place during said process, alter the structure of the pigment. Heating the dried coating film to above the glass temperature of the pigment leads to a pronounced relaxation, i.e. the pitch of the helix of the cholesteric liquid crystal is shortened and hence the reflection wavelength of the pigment is shifted toward shorter wavelengths; there is a blue shift. If, then, the glass temperature of the pigment is above the relatively low processing temperature of the coating material, relaxation does not occur completely, and the result is a color which is different from that of coating films which have been prepared at temperatures above the glass temperature and which hence correspond in their color to the completely relaxed material.